To learn more about why deleting large objects is slow in Redis, read this quick overview
To delete a large set in Redis:
Rename the key to a unique, namespaced key so that the set appears “deleted” to other Redis clients immediately.
Incrementally delete members from the set in small batches until it is empty. By limiting the size of our delete commands, we ensure that we don’t block the server for too long.
Please note that the following code doesn’t gracefully handle Redis connection failures. If any Redis command fails and raises an exception, you’ll need to clean up manually.
# Rename the key
newkey = "gc:hashes:" + redis.INCR("gc:index")
redis.RENAME("my.set.key", newkey)
# Delete members from the set in batches of 100
cursor = 0
loop
cursor, members = redis.SSCAN(newkey, cursor, "COUNT", 100)
if size of members > 0
redis.SREM(newkey, members)
end
if cursor == 0
break
end
end
$redis = Redis.new
def delete_set(key)
# Rename the key
newkey = "gc:sets:#{$redis.incr("gc:index")}"
$redis.rename(key, newkey)
# Delete members from the set in batches of 100
cursor = "0"
loop do
cursor, members = $redis.sscan(newkey, cursor, count: 100)
$redis.srem(newkey, members) if members.size > 0
break if cursor == "0"
end
end
# Example:
#
# delete_set("my.large.set")Here are some example implementations of the above using background jobs in Ruby: